Last thing I knew, most of michigan was too far north to take advantage of WAAS. It is only on two sats that are over the equator. Plus, it's not effective in trees. And, you need to be w/in 200 miles of a reference station, none of which are in MI.
My e-trex legend has WAAS, but I have it disabled because I dont notice a increase in accuracy and it uses more power.
WAAS, from what I understand is mostly for aviation and nautical use.